From: Oleg Nesterov Date: Mon, 10 Nov 2008 14:39:30 +0000 (+0100) Subject: fix for account_group_exec_runtime(), make sure ->signal can't be freed under rq... X-Git-Tag: v2.6.28-rc5~79^2~1 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ad474caca3e2a0550b7ce0706527ad5ab389a4d4;p=pandora-kernel.git fix for account_group_exec_runtime(), make sure ->signal can't be freed under rq->lock Impact: fix hang/crash on ia64 under high load This is ugly, but the simplest patch by far. Unlike other similar routines, account_group_exec_runtime() could be called "implicitly" from within scheduler after exit_notify(). This means we can race with the parent doing release_task(), we can't just check ->signal != NULL. Change __exit_signal() to do spin_unlock_wait(&task_rq(tsk)->lock) before __cleanup_signal() to make sure ->signal can't be freed under task_rq(tsk)->lock. Note that task_rq_unlock_wait() doesn't care about the case when tsk changes cpu/rq under us, this should be OK. Thanks to Ingo who nacked my previous buggy patch. Signed-off-by: Oleg Nesterov Acked-by: Peter Zijlstra Signed-off-by: Ingo Molnar Reported-by: Doug Chapman --- Reading git-diff-tree failed